title: Survival of Listeria monocytogenes during Production and ripening of traditional Turkish Savak tulum cheese and in synthetic gastric fluid.
abstract: This study investigated the survival and acid tolerance of Listeria monocytogenes during the 2-day processing stage and 90-day ripening of Savak tulum cheese, a traditional cheese in Turkey. Experimental Savak tulum cheese was produced from raw sheep's milk that was inoculated with a L. monocytogenes mixture consisting of five strains (average 7.0 log CFU/ml) and was ripened at 6°C for 90 days. Microbiological and chemical analyses and acid exposure experiments in synthetic gastric fluid (SGF) (pH 1.5 to 2.5) were carried out on days 1 and 2 during processing and on days 0, 15, 30, 45, 60, and 90 during ripening. The numbers of L. monocytogenes did not decrease during processing, but a total of 4.1 log CFU/g reduction was observed during ripening. Throughout the ripening period, L. monocytogenes cells survived direct 90-min exposures of the cheese samples to SGF. These results suggest that, although the pathogen numbers decreased in Savak tulum cheese ripened at 6°C for 90 days, a sublethal environment may have occurred in the cheese during the production stage, activating the acid-tolerance mechanisms of the pathogen and allowing L. monocytogenes to maintain its viability in the SGF for 90 min.
authors.affiliation: Department of Food Engineering, Faculty of Engineering, Tunceli University, 62100 Tunceli, Turkey;, Email: adikici@tunceli.edu.tr.
authors.forename: Abdullah
authors.initials: A
authors.lastname: Dikici
authors.forename: Mehmet
authors.initials: M
authors.lastname: Calicioglu
mesh_terms: D000818:Animals; D002611:Cheese / Q000032:analysis / Q000382:microbiology*; D015169:Colony Count, Microbial; D005506:Food Contamination / Q000032:analysis*; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D005744:Gastric Acid / Q000378:metabolism; D008089:Listeria monocytogenes / Q000254:growth & development*; D050296:Microbial Viability; D012756:Sheep; D013997:Time Factors; D014421:Turkey